97 E420 Key button doesn't lock/unlock doors?
 

I have a 97 E420. One of my keys work but the other doesn't lock/unlock doors. Do the keys have batteries that can be replaced? Or am I unlucky and have to replace the switchblade key?

IF you hold down the button for 5-6 seconds do you see the LED in the red window blink on the key?

Yes, the key does have replaceable batteries.

No LED blinking, how do I open the W210 key?

There are no instructions in my manual.

Got it, you just pry it open.

You may have to synchronize the key after replacing the battery, because it has sat with it dead. That procedure is also in your manual.

If you quickly replace an old but still good battery, it will retain synchronization.

Yours is similar to mine, and the sync procedure may be the same. Aim at the sensor and press the button briefly twice, then within 30 seconds, insert the blade into the ignition lock and turn to position 2.

On another note, my key went through the washer recently. Upon getting it back all wet, I pulled the battery and put the key in a baggie of rice for a few days to dry it out. I was surprised but very glad that it still worked. The last key that I bought cost $240.

Thanks, Matt, will do. Wow $240, that's beyond absurd.

Yes, very expensive, but that's with the remote fob. If I could buy a master key or a valet key today, I would, but the dealer does not sell them.

I forgot to note that I did blow the wet key out with compressed air before the rice treatment. That probably helped as well. A lot of water came out with the compressed air.